.300 and AR mags

[interceptor]

After studying AR mags, I'm wondering: is modification of the mag body itlesf is necessary to load .300 Whisper rounds? I know the feed lips are in the right place already, right? But what of the creases is the mag body, especially the deep one in the front? Seems to me that it will contact the bullet itself?

[jjmcrowell]

I set my OAL based on the contact of the bullet with the deep track/crease, If I load to magazine length with 220 gr HPBT, the rounds don't sit real well in the magazine. So a little shorter OAL allows 100% function in my rifle.

Accuracy might be hurt a little by not loading as close to the lands as possible, but I feel better when all the rounds sit just right in the magazine.

Maybe with some of the VLD type bullets, I could load out to magazine length. Still playing with it right now though.

I think this is what your talking about...
http://www.quarterbore.net/forums/photopost/data/535/DSC08128.JPG

[320pf]

Interceptor

jjmcrowel is right on correct. I have about 4 30-round mags that work very well with the bullets seated out the the max mag length, but all of my mags. work with 300 fireball ammo. The diameter of bullet rides where if rides on the front ridge is about 0.3 in. But, if I want the most reliable feeding from the mag., I seat the bullet deeper so diameter at the point of contact on the ogive is 0.245-0.250 in. This is about the same as the outside diameter of a 223 neck... which is the part on the cartridge that contacts the forward ridge in AR mags. However, for the heavier bullets this is not always possible. So my suggestion is test your mags. to find the ones that work best.

An additional note, I have upgraded all my mags. with "MagPul" followers and heavier springs. This really improved the overall performance of all of my mags. for both 300 fireball and 223

320pf

[interceptor]

Well, I'm close then. All of my mags already have grey MagPul followers and chrome silicone springs. Part of my reliability thing for 3-gun and multi-gun.

Come on brass, hurry up and land on my doorstep!!

[320pf]

Interceptor,

If you really want to try out your new toy. Go buy a box (20 rd) of 221 Fireball... pull the bullets and dump the powder. I am assuming that you have Redding dies, There should be two tapered expander balls. One will take 221 Fireball brass from 0.224 to 0.270 or 0.280 (7mm) and the larger one will neck it up to 0.308. Then you will have 20 rds (40 if you spring for two boxes) to start you load development.

I could not wait either so that is what I did. :)

I am currently making my own brass from either 223 or 221 Fireball brass.

320pf

[interceptor]

Yeah, I could do that...:rolleyes: Just gotta find my bullet pull'r. Wait a minute, I've got a 100 pack of band new Remington .221 brass at work. If they don't come in tomorrow I'll get them.

And yes, I do have the Redding die set, the two die set.

[interceptor]

Wait a minute. Why don't I just make them out of .223's? I've got 500 or so here on hand?

Just have to find my case trimmer and deburring tool... Now where did I ...:confused:

[interceptor]

Back to the original line of thought here. I'm assuming everyone is using and referring to the GI type steel and aluminum mags. What about the polymer mags, Israeli type IIRC. Suppose it'd be possible to pull the baseplate, spring, and follower and with it laying on it's side use a flat filie to enlarge the i.d. of the mag body at the front crease, from the inside ? If it worked, then we could seat 200-240gn out to the magazine length. I know we've got a few used ones at the shop I could tinker with...


BTW, built a homemade 5 rounder last night. Used a OEM Bushy blocked 10 rounder, cut flat with the mag well, removed one coil, kept the green g.i. follower. Dissappears once it's seated.